Defect engineering of ZnO

• Published in: Applied surface science 2008-10, Vol.255 (1), p.68-70
• Main Authors: Weber, M.H., Selim, F.A., Solodovnikov, D., Lynn, K.G.
• Format: Article
• Language: English
• Subjects: Chemical composition analysis, chemical depth and dopant profiling; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Defect engineering; Defects and impurities in crystals; microstructure; Depth profiles; Exact sciences and technology; Materials science; Materials testing; Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity); Optical constants: refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of bulk materials and thin films; Other interactions of matter with particles and radiation; Physics; Point defects (vacancies, interstitials, color centers, etc.) and defect clusters; Positron annihilation; Structure of solids and liquids; crystallography; ZnO
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2008.05.170

The defect responsible for the transparent to red color change of nominally undoped ZnO bulk single crystals is investigated. Upon annealing in the presence of metallic Zn as reported by Halliburton et al. and also Ti and Zr a native defect forms with an energy level about 0.7 eV below the conduction band. This change is reversible upon annealing in oxygen. Optical transmission data along with positron depth profiles and annealing studies are combined to identify the defect as oxygen vacancies. Vacancy clustering occurs at about 500 °C if isolated zinc and oxygen vacancies. In the absence of zinc vacancies, clusters form at about 800 °C.